1. Field of the Invention
The present invention is directed generally to light induced fluorescence techniques for the detection of substances. More particularly, the invention is directed to a handheld, non-contact illumination and detection device for identifying the presence or absence of specific substances including explosives, illegal drugs, chemical/biological agents, and toxic industrial chemicals.
2. Description of the Related Art
As described in the Guide for the Selection of Drug Detectors for Law Enforcement Applications, NIJ Guide 601-00, by Parmeter et al., Contraband Detection Technologies Department Sandia National Laboratories (1999) which is incorporated herein by reference in its entirety, trace detection is a common approach to the detection of narcotics, and refers to detecting the drug by collection and analysis of microscopic amounts of the drug. These microscopic quantities can be in the form of vapor, particulate, or both.
There are two primary methods of collecting trace material for delivery to a trace chemical detector: vacuuming and swiping. Vacuuming is used to collect vapor and/or airborne particulate and is usually performed with a hand-held device similar to a Dustbuster. Air is pulled through a filter pad within this device, collecting vapor or particles of illicit drugs that are present in the air. The pad is then removed and presented to a sampling port on the trace detector for analysis. A few trace detectors are designed so that air can be sucked directly into an inlet port on the detector.
Swipe collection, which is intended to collect particulate residue deposited on surfaces uses sampling pads that are wiped (“swiped”) across a surface to be analyzed. These pads are usually supplied by the manufacturer of the detector used and can be applied to any surface, including clothing and skin. Once a swipe sample has been obtained, the pad is presented to a sampling port on the detector, usually in the same way as that of a vacuum sampling pad. Swiping is often more sensitive than vacuuming because it allows more particulate matter to be collected, and with low vapor pressure materials even one microscopic particle may contain a larger mass of material than would be present in a large volume of air saturated with vapor. However, swiping may sometimes be considered too invasive for purposes of personnel screening because it requires direct contact of the sampling pad with skin or clothing.
Additionally, trained canines are also used as initial trace detectors because they detect drugs from residual vapor and particle contamination.